Question

7. A stone is dropped from a cliff, the time during which it covers a distance of 490 m is
a. 10 sec
b. 100 sec
c. 9.8sec
d. 980 sec
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Answer 1

Explanation:

the stone that is dropped from the top of a cliff 490 m high, s = 490, a = 9.8 and u = 0.

Substituting these values gives:

490 = 0*t + (1/2)*9.8*t^2

=> t^2 = 490*2/9.8

=> t^2 = 100

=> t = 10 s

Answer 2

Explanation:

Here height h = 490 m

we know that:

h = ut + 1/2 g t^2

490 = 0 x t + 1/2 × 9.8 t^2

490 = 4.9 t^2

Therefore , t^2 = 490 / 4.9 = 100

t^2 = 100

t = square root of 100

t = 10 seconds. Ans.

Here, u= Initialvelocity = 0

height h = 490 m

g = 9.8 m s ^-2 .